Recently, standardization for introducing a device to device (D2D) communication service to a cellular communication system based on a licensed band has been in progress. In D2D communication, a terminal may directly communicate with another terminal without passing through a network (e.g., a base station).
Meanwhile, if terminals that are spatially adjacent perform D2D communication, the terminals may be controlled by a cellular base station, but only minimal help may be provided to the terminals, or no help from a cellular base station may be provided to the terminals.
Control by a base station means that the base station provides resources to devices in a centralized manner and in a contention-free manner. Accordingly, control by the base station may maximize throughput.
In contrast, if only minimal help is provided to a terminal or no help from a base station is provided to the terminal, it is difficult for resources to be scheduled in a centralized manner.